The present invention relates to torque transmitting and torsion damping apparatus, especially to improvements in torque transmitting and torsion damping apparatus which can be utilized in motor vehicles to compensate for fluctuations of torque which is transmitted between driving and driven components, particularly between the crankshaft of the internal combustion engine and the input shaft of the change-speed transmission in a passenger car or another motor vehicle.
It is already known to provide a torsion damping apparatus, which is installed in a motor vehicle between the crankshaft of the internal combustion engine and the input shaft of the change-speed transmission, with several flywheels which are rotatable relative to each other within certain limits and against the opposition of one or more dampers. Such apparatus are disclosed, for example, in commonly owned copending patent application Ser. No. 669,657, now abandoned, of Oswald Friedmann as well as in several other pending applications of the assignee. The flywheels can rotate relative to each other about the axis or axes of one or more bearings. A friction clutch is interposed between the last flywheel and the input shaft of the transmission, and such friction clutch includes a disc which is movable into and out of friction- and heat-generating engagement with the adjacent flywheel. This can adversely influence the operation and useful life of the bearing, especially if the races of the bearing are directly connected to or in direct contact with the adjacent flywheels. Thus, one race of an antifriction ball bearing between two coaxial flywheels which can move angularly relative to each other against the opposition of one or more dampers can be non-rotatably secured to one of the flywheels, and the other race of the bearing can be non-rotatably secured to the other flywheel. It has been found that the just described mounting of the flywheels on an antifriction bearing enables the damper or dampers to produce a highly satisfactory damping action. Nevertheless, such torsion damping apparatus failed to gain popularity in the automotive and other industries, primarily because the useful life of the bearing or bearings between the flywheels is relatively short. The bearing or bearings are one of the critical elements in these torsion damping apparatus so that their failure after a relatively short interval of use deters the manufacturers of motor vehicles from employing such torsion damping apparatus between the engine and the change-speed transmission.
A torque transmitting and torsion damping apparatus between the input shaft of a change-speed transmission and the output shaft of an engine must be capable of taking up stresses, such as those attributable to fluctuations of transmitted torque, which develop while a rotary driving element transmits torque to a rotary driven element. As a rule, or in many instances, the crankshaft of the engine is attached directly to a first flywheel, the input shaft of the transmission can receive torque from a second flywheel by way of a friction clutch, and the means for transmitting torque between the flywheels comprises one or more dampers which oppose angular movements of the flywheels relative to each other. The second flywheel has a friction surface which is engaged by a lining of the clutch disc of the friction clutch when the latter is engaged to transmit torque from the second flywheel to the transmission. The bearing or bearings between the flywheels have pairs of races confining single or multiple rows of antifriction rolling elements in the form of needles, balls, rollers or the like. The bearing or bearings enable the torque transmitting and torsion damping apparatus to perform a highly satisfactory damping of oscillations which develop in the power train between the engine and the transmission. Nevertheless, and as already stated above, such apparatus failed to gain widespread acceptance due to the short useful life of the bearing or bearings. As a rule, the bearing or bearings constitute the first part or parts which require replacement, and such replacement must take place after a relatively short period of use.
One of the main reasons that the useful life of the antifriction bearing or bearings between the flywheels of the above outlined torque transmitting apparatus is relatively short is that the bearings are subjected to pronounced thermal stresses, primarily because the friction clutch between the input element of the change-speed transmission and the respective flywheel invariably generates heat when it is called upon to transmit torque to the transmission.
The damper or dampers which are provided between the relatively movable flywheels of the just outlined torque transmitting apparatus normally comprise at least one set of coil springs or analogous energy storing elements which yieldably oppose angular movements of the flywheels relative to each other, as well as one or more friction generating devices each of which can oppose some or all angular movements of the flywheels relative to one another. The damper or dampers contribute significantly to the initial and maintenance cost of the torque transmitting apparatus.